Investigation of Noise Level and Spatial Resolution of CT Images Filtered with a Selective Mean Filter and Its Comparison to an Adaptive Statistical Iterative Reconstruction

Introduction: A simple noise reduction algorithm, i.e. a selective mean filter (SMF), had been previously introduced. The aim of this study is to investigate the image qualities filtered by a SMF and its comparison to an adaptive statistical iterative reconstruction (ASIR). Material and Methods: To assess the basic image quality, an American Association of Physicists in Medicine Computed Tomography (AAPM CT) performance phantom was used. The phantom was scanned by ۱۲۸ Multiple Slices Computed Tomography. The tube current varied from ۵۰ mA to ۱۰۰, ۱۵۰, and ۲۰۰ mA. The images of a phantom were reconstructed by filtered back projection (FBP) followed by SMF and ASIR (۲۰, ۴۰, ۶۰, ۸۰, and ۱۰۰%). The image quality assessment was in terms of noise level, noise power spectrum (NPS), and modulation transfer function (MTF). Results: The noise level and NPS of SMF was similar with ASIR ۱۰۰%. The values of the MTF۱۰ of the ASIR filter at any level and SMF were comparable. The MTF۱۰ values of ASIR ۶۰%, and SMF with ۵۰ mA (low) were ۰.۷۶ ± ۰.۰۲ and ۰.۷۵ ± ۰.۰۲ cycle/mm, respectively. Meanwhile, the MTF۱۰ of ASIR ۶۰% and SMF with ۲۰۰ mA (high) were ۰.۷۴ ± ۰.۰۰ and ۰.۷۳ ± ۰.۰۰ cycles/mm, respectively. Conclusion: Our results indicated that the performance of the SMF in reducing noise is equivalent to the maximum level of ASIR strength, i.e., ASIR ۱۰۰%.

کلیدواژه ها:

Computed Tomography ، Image Quality ، Algorithms ، Image Processing ، selective mean filter ، adaptive statistical iterative reconstruction